graphic: 0.731
device: 0.638
semantic: 0.621
other: 0.617
performance: 0.601
files: 0.527
permissions: 0.526
debug: 0.458
network: 0.377
boot: 0.365
PID: 0.353
vnc: 0.346
socket: 0.316
KVM: 0.171

errors which can't backing storage for guest RAM with -mem-path

I found it can't backup the guest RAM when i run simple ram test code with 

errors which can't backing storage for guest RAM with integratorcp, the commander is:

qemu-system-arm -M integratorcp -m 1 -semihosting -nographic -mem-path mem.txt -kernel build/emu_ram_test.elf

i wrote the patter "0x55" to all of the rest of RAM in my test, after run my test code, it just generate the 1048576 Bytes file, i split these file into 2kB, most of split file is black, some of them just display \00 after open with gedit.

i don't know whether my commander is incorrect, anyone can confirm it for me? i just want to write the guest RAM and read it from host during the guest code is running. but my guest just has simple os without file system and network. so i want to try with this backend RAM ways.

thanks.
js

The memory region mapped by QEMU for -mem-path is configured such that changes are private to the QEMU process.

If you need an external process to be able to view memory changes, you need to use the modern "memory-backend-file" class with -object arg, and specify  share=on to make the data visible to non-QEMU processes.